1. Field of the Invention:
The present invention relates to the preparation of hydroxybenzaldehydes, and, more especially, to the preparation of hydroxybenzaldehydes by hydrocarbonylation of the corresponding halophenols.
2. Description of the Prior Art:
U.S. Pat. No. 3,960,932 describes a general process for the preparation of aldehydes by reacting aryl or vinyl halides, or halides of heterocyclic compounds, with a mixture of carbon monoxide and hydrogen in the presence of a tertiary amine and of a palladium catalyst consisting of a complex of a divalent palladium derivative with a phosphine, a phosphite or an arsine of the combination of a divalent palladium salt, or of finely divided metallic palladium, with a complexing agent of the phosphine, phosphite or arsine group. The aryl halides employed in the process described in U.S. Pat. No. 3,960,932 are phenyl or naphthyl bromides or iodides, unsubstituted or substituted by alkyl, alkoxy, nitrile or alkyl carboxylate groups.
European Patent EP No. 109,606 describes increasing the kinetics of the hydrocarbonylation reaction of the above process, by carrying out such reaction at pressures of 2 to 40 MPa (20 to 400 bar), at temperatures of 80.degree. C. to 250.degree. C., and by employing large amounts of phosphine or of phosphite (2 to 10.sup.5 times the molar quantity of catalyst).
It will of course be appreciated that these processes of the prior art do not relate to the hydrocarbonylation of halophenols.